METHOD FOR ULTRASONIC FLAW DETECTION OF FILLET WELDED PART

PURPOSE:To enhance flaw detection capacity, by interposing a wedge wherein the angle formed by surface thereof is set to a proper one using two vertical probes for transmission and reception. CONSTITUTION:One surface of a wedge wherein the angle formed by two surface thereof is set to theta is placed on the welded bead 2 of a fillet welded part wherein the angle formed by the surface of a member 1 to be inspected where the presence of a planar flow 3 is estimated and the surface thereof is alpha. Herein, a contact medium is applied between the bead 2 and the wedge 4, Further, the angle theta of the wedge 4 is set by formula sintheta/sinalpha=va (the longitudinal wave speed in the wedge 4)/vb (the longitudinal wave speed in the bead 2) corresponding to the angle alpha of the bead 2. Then, the ultrasonic wave from a transmitting probe 5 is allowed to advance through the wedge 4 and the bead 2 to be allowed to vertically impinge against the flaw 3 and the reflected wave therefrom is received by a receiving probe 6 to detect the presence of the flaw 3. Therefore, a large reflected wave is returned from the flaw 3 in the vertical direction and the vertical direction and the effect of the multiple reflection wave in the wedge 4 is suppressed and even the small planar flow directly under the bead can be cen be certainly detected.